Burner arrangement for a combustion system for combusting liquid fuels and method for operating such a burner arrangement

ABSTRACT

A burner arrangement for a combustion system for combusting liquid fuels including a burner hub, at least one air supply channel and at least one fuel supply channel for each fuel type is provided. The at least one fuel supply channel is embodied at least partially in the burner hub, with a flow divider arranged in at least one fuel supply channel, which is distanced from the wall of the fuel supply channel so that an interspace associated with the flow path of the fuel flowing through the fuel supply channel is formed between the wall of the fuel supply channel and the flow divider. A method for operating such a burner arrangement is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of European Patent Office applicationNo. 09162827.1 EP filed Jun. 16, 2009, which is incorporated byreference herein in its entirety.

FIELD OF INVENTION

The invention relates to a burner arrangement for a combustion systemfor combusting liquid fuels and method for operating such a burnerarrangement with the features cited in the preambles of the respectiveindependent claims.

BACKGROUND OF INVENTION

With respect to universal efforts to reduce the pollutant emissions ofcombustion systems, particularly in gas turbines, burners were developedover the last few years which have particularly minimal nitrogen oxide(NOx) emissions. Considerable importance is attached here to suchburners not only being operable with one fuel, but instead as far aspossible with various fuels, for instance oil, domestic gas and/or coalgas or in combination, in order to increase the supply reliability andflexibility of the operation. Such burners are described for instance inEP 0 276 696 B1.

One problem with the design of burners for all possible differentoperating conditions and operating materials consists in the volume ofthe individual operating materials needed during operation beingdifferent in each instance so that it becomes difficult for alloperating materials to use the same supply system and the same injectionopenings. It is therefore known in the prior art to use different supplysystems for liquid and gaseous mediums.

A further problem nevertheless also arises if gaseous fuels are thenoptionally also to be used with completely different specific fuelvalues, for instance natural gas and coal gas. The different relativevolume ratios when using these two fuels and the different chemicalprocesses during their combustion require a modification or extension ofthe known systems.

It is known for inert substances, in particular water or water vapor, tobe injected in order to reduce the pollutant emissions in certainoperating states, as a result of which the combustion temperature isreduced and the Nox pollutant emissions are consequently lowered. WO89/08803 A1 also discloses that with the use of heavy oils as fuel, forexample, admixtures should also be mixed with the injected substances inorder to prevent damage to components of a subsequent gas turbine.

EP 0 276 696 B1 discloses a hybrid burner for premixing operation withgas and/or oil, like is used in particular for gas turbine systems. Theburner consists of a central pilot burner system, which can be operatedwith gas and/or oil as a so-called diffusion burner or a separate premixburner. Provision is also made for the possibility of feeding inertsubstances. The pilot burner system is surrounded by a main burnersystem, which has an air supply annular channel system with a helicalblading located therein having a plurality of blades for the premixingoperation with gas. Inlet nozzles for oil are also present in the regionof the helical blading in the main burner system, thereby enabling themain air flow to be premixed with oil.

DE 42 12 810 B4 and EP 0 580 683 B1 emanating therefrom describe theprior art closest to the present invention. It is assumed here that whencombusting combustion gas with a low fuel value, no special measures areneeded to reduce the pollutant emission, since when combusting suchgases, no excessively high flame temperatures occur and the formation ofNox therefore remains practically insignificant. It is thereforesufficient to create a further simple supply system, with attentionhaving to be paid to ensuring that this system does notdisadvantageously influence the other systems and does not reduce theoperational reliability during operation of the other systems. It istherefore important for the further annular channel to open for theother fuels on the inflow side above the outlet nozzles. In this way, noignitable mixture can reach the further annular channel if the burner issupplied with a different type of fuel through the outlet nozzles.

One challenge with these burners emerges as a result of the mechanicalstresses in the walls of the metallic housing, the so-called hub, whichoccur due to an uneven thermal distribution, in which hub the supplyannular channels of the gas and oil energy carriers, are arrangedrelatively close to one another. An annular gas compartment supplies themain burner in respect of the flow direction of the inflowing air on theinput side upstream of the so-called helical blades, which convey amixed helix to the air flow with the combustion gas or through thehelical blades. An oil supply is also available as the gas supply, whichis generally arranged in the vicinity of the burner outlet. It includesan annular oil compartment, and an oil supply channel leading to theannular compartment, which is arranged in the hub wall located betweenthe annular gas compartment and the pilot burner.

As gas has a lower density than oil, it requires a larger cross-section,as a result of which the dimensioning of the gas supply is considerablylarger than the oil supply. The part of the burner hub with the gassupply therefore has a larger external surface facing the air channelthan the oil supply. The air supply takes place with precompressed air,which has passed through a compressor, as a result of which thissupplied air has a temperature, as a result of the compression, whichalready reaches above 400° C. The region of the burner hub with the gassupply is consequently rapidly heated to a temperature in the region ofabove 400° C. and remains at this operating temperature. The oil supplychannel leading to the annular oil compartment is by contrast distancedfar from the hot air supply channel so that the oil in the oil supplychannel barely experiences any heating and thus only has a temperatureof approximately 50° C.

As, on the one hand, the burner hub experiences a strong heating in theregion of the annular gas compartment and, on the other hand, theadjacent oil supply channel is considerably cooler, the wall between theannular gas compartment and the oil supply channel is subjected to alarge temperature gradient both during continual operation and also whenflushing out the burner hub. If the hub, i.e. the oil channel, isflushed with water, the gas channels remain hot and the oil channelcools down significantly. The channels are very close to one another asa result of the limited space in the hub and high temperature/thermalgradients result. As a result of the temperature gradient, thermalstresses result, which significantly shorten the service life of suchburner hubs.

SUMMARY OF INVENTION

The object of the present invention is thus to reduce the describedthermally specific stresses in the burner hub during operation and whenflushing the hub of the burner arrangement.

This object is achieved by a burner arrangement as claimed in the claimsand/or a method for operating such a burner arrangement as claimed inthe claims. The dependent claims contain advantageous embodiments of theinvention.

An inventive burner arrangement for a combustion system for combustingliquid fuels includes a burner hub, at least one air supply channel andat least one fuel supply channel for each type of fuel. The at least onefuel supply channel is embodied at least partially in the burner hub, sothat the material of the burner hub forms a wall of the fuel supplychannel. In accordance with the invention, a flow divider is provided inat least one fuel supply channel, said flow divider being distanced fromthe wall of the fuel supply channel so that an interspace associatedwith the flow path of the fuel flowing through the fuel supply channelis formed between the wall of the fuel supply channel and the flowdivider.

In the inventive burner arrangement, the interspace forms a regionassociated with the flow path, in which an adjustable continual fuelflow flows. This fuel flow prevents deposits from forming in theinterspace and thus prevents a blockage of the nozzles through which thefuel escapes. Furthermore, the flow in this region decouples the hotstructure from the cold structure and thus represents a heat shield. Asa result of the reduced thermal transfer, the thermally specificstresses reduce compared with the burner arrangements without a flowdivider.

In the inventive burner arrangement, the flow divider consists of aflow-through means, in particular a pipe with a flow-through opening,and a disk with a corresponding flow-through opening. A central bore inthe center of the flow divider is preferably provided as a flow-throughopening. The majority of the fuel flows through this central bore.

When viewed in the flow direction, the disk is also provided at thefirst end on the flow-through means.

In a preferred embodiment, the disk has a larger diameter than thediameter of the flow-through means. The disk can be clamped here in thewall of the fuel supply channel. Positioning means, e.g. a positioningprojection, can however also be provided on the wall of the fuel supplychannel.

The flow divider in the disk preferably has at least one bore. The diskalso has several bores, which are essentially distributed equally overthe periphery. These bores route a small part of the preferably coldfuel flow into the interspace, with the hot carrier structure thus beingthermally decoupled from the inflowing cold fuel. The heat transfer inthis region is thus reduced.

According to a further aspect of the present invention, said object isachieved by a method for operating such a burner arrangement, with,during operation, fuel being routed through the fuel supply channel,with the majority of the fuel flowing through the flow-through openingof the flow divider and a small part of the fuel flowing through theinterspace of the flow divider, thereby largely preventing deposits inthe interspace.

A small part of the flow is thus routed through the interspace and thusprevents the formation of deposits in the interspace, in other words,above all on the wall of the carrier structure of the combustion chamberhub. A blockage of the nozzles is thus prevented.

Through the minimal flow, a function as a heat protection shield isprovided, since the hot carrier structure is thermally decoupled fromthe inflowing cold fuel, in particular from cold oil. The main flow forsupplying the nozzles flows through the flow-through opening of the flowdivider, with this flow-through opening preferably being provided as alarge, central bore in the center of the flow divider. High temperaturesand stress gradients therefore no longer form. A significant increase inthe service life is the desired result.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, properties and advantages of the invention result fromthe following description of an exemplary embodiment with reference tothe appending figures, in which;

FIG. 1 shows a burner arrangement known from EP 0 580 683 B1,

FIG. 2 shows a partial cross-sectional view through a known burnerarrangement,

FIG. 3 shows a basic diagram of an inventive helical blade with twointegrated gas stages which can be controlled independently of oneanother,

FIG. 4 shows a basic diagram of a burner chamber hub with two integratedgas stages, which can be controlled independently of one another and anoil channel,

FIG. 5 shows a burner chamber hub 18 with an inventive flow divider 40,

FIG. 6 shows an inventive flow divider 40.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a burner arrangement 20 as claimed in the prior art, which,if necessary in conjunction with several similar arrangements, can beused in the combustion chamber of a gas turbine system for instance.

It consists of an inner part, the pilot burner system and an outer part,the main burner system, which is disposed concentrically thereto. Bothsystems are suited to operation with gaseous and/or liquid fuels in anycombination. The pilot burner system consists of a central oil supply 1(medium G) and an inner gas supply channel 2 (medium F) arrangedconcentrically around the latter. This is in turn surrounded by an innerair supply channel 3 (medium E) which is arranged concentrically aroundthe axis of the burner.

A suitable ignition system can be arranged in or on this channel, forwhich many embodiment possibilities are known and the representationthereof was therefore omitted here. The central oil supply 1 has an oilnozzle 5 at its end and the inner air supply channel 3 has a helicalblading 6 in its end region. A pilot burner system 1, 2, 3, 5, 6 can beoperated in a manner known per se, i.e. predominantly as a diffusionburner. Its task is to keep the main burner stable during combustion,since this is mostly operated with a lean mixture which tends towardsinstabilities.

The main burner system has an outer air supply annular channel system 4which is arranged concentrically with respect to the pilot burner systemand runs obliquely thereto. This air supply annular channel system 4 isalso provided with a helical blading 7. The helical blading 7 consistsof hollow blades with outlet nozzles 11 in the flow cross-section of theair supply annular channel system 4 (medium A). These are fed from asupply line 8 and an annular channel 9 through openings 10 for themedium B. The burner also has a supply line 12 for a medium C,preferably oil, which opens into an annular channel 13, which has outletnozzles 14 for the medium C in the region or below the helical blading7.

A spray jet 15 of the medium C is also shown. In accordance with theinvention, the burner also has a further coal gas supply channel 16 formedium D. This opens into the outer air supply annular channel system 4,just above the helical blading 7 with the outlet nozzles 11, and on itsinternal side, so that in principle both together form a diffusionburner.

FIG. 2 shows an enlarged partial cross-sectional view through a knownburner hub 18 as claimed in the prior art. The burner arrangement iscircular, so that the annular channel 9 and 13 can also be representedas circular.

The region of the main burner in FIG. 1 can also be realized similarly.The helical blades 9 only have a supply channel with the outlet nozzles11, which are preferably provided to inject a gaseous medium B. Anoutlet nozzle 14 for injecting preferably liquid medium V is providedtherebelow in the flow direction. A plurality of outlet nozzles 14 isarranged along the circular annular channel 13, so that the injection ofthe medium C can take place equally in the similarly circular combustionchamber.

Contrary to FIG. 1, this representation nevertheless only has one gassupply line and one oil supply line.

FIG. 3 shows a basic diagram of a helical blade 7 with two integratedgas stages B and D which can be controlled independently of one another.

The helical blade 7 has two supply channels 11 and 21 which areindependent of one another. The one supply channel with the outletnozzles 11 can be used to inject the medium D for instance and thesecond supply channel 21 can be used to inject the medium B by way ofthe outlet nozzles 24. Both mediums to be injected through the supplychannels of the helical blade 7 are preferably gaseous, e.g. the onenatural gas and the other coal gas. An inert substance such as watervapor for instance can similarly be injected by way of these outletnozzles 11 and/or 21 as required.

FIG. 4 shows a fuel hub 18 with the supply channel 16, the annularchannels 9 and 13 and openings 10, which lead the fuel into the blade 7.

If the supply channel 12, subsequently referred to as oil channel 12, isflushed with water, different temperature distributions result. The twogas supplies remain hot and the oil channel 12 cools down significantly.The adjusting high thermal gradients between the flushed oil channel andthe heated gas passages reduce the service life of the fuel hub 18.

FIG. 5 shows an inventive fuel hub 18 with a flow divider 40. The flowdivider 40 (FIG. 6) consists of a pipe 45 with a flow-through opening 55(subsequently referred to as pipe opening 55). A disk 42 is attached tothe first end of the pipe 45 when viewed in the flow direction. The disk42 likewise has a pipe opening 55, which corresponds to the pipe opening55. The diameter of the disk 42 is larger than the diameter of the pipe45. As a result, an interspace 38 font's in the flow direction betweenthe wall 21 and the pipe 45, so that the flow divider almost adopts theform of a double pipe, namely the pipe 45 and the wall 21, which islikewise embodied here in the manner of a pipe. The disk 42 canessentially be attached e.g. clamped to the wall 21 in a faun-fitmanner. The embodiment of a positioning projection 35 is also possible,on which the disk 42 rests. Bores 50 are attached in the disk 42. Thesebores 50 are preferably evenly distributed over the periphery. As aresult of the bores in the flow divider 40 attached above the disk 42, afluid flow is divided. An adjustable small part of the flow is routedthrough these smaller bores 50 into the interspace 38. This fluid flowthus prevents the formation of deposits in the interspace 38 and ablockage of the nozzles 14. The minimal flow also functions as a heatprotection pipe. In addition, the reduced flow in this region decouplesthe hot structure from the code and thus represents a heat shield. Thehot carrier structure is thus thermally decoupled from the inflowingfuel, preferably cold oil. The main flow for supplying the nozzles 14also flows through the pipe opening 55. This is preferably realized as acentral bore in the center of the flow divider 40. As a result of theflow divider 42 and a minimal flow of the fuel in the interspace 38, thethermal transfer a in the interspace is essentially less than thethermal transfer α_(previous) without the flow divider at the samepoint; therefore α<<α_(previous). The main flow for supplying the nozzle14 nevertheless also flows through the central bore, in other wordsthrough the pipe opening 55. The thermal transfer α essentially remainsunchanged here, i.e. α≈α_(previous).

As result of the minimal flow in the interspace 38, the flow divider 40therefore functions as a heat protection shield and the hot carrierstructure is thus decoupled from the inflowing cold oil. Hightemperature and tensile gradients therefore no longer form. The servicelife of the combustion chamber hub 19 is thus significantly increased.

The inventive flow divider 40 thus divides the fluid flow namely into aminimal flow, which flows through the interspace 38 and a quantitativemain flow, which flows through the pipe opening 55. The flow divider 40thus prevents deposits and a blockage of nozzles when using liquidfuels. The reduced flow also decouples the hot structure from the coldand thus represents a heat shield. Furthermore, high thermal gradientsand thermal stresses resulting therefrom are prevented by way of aminimal cross-section. With the use of the flow divider 40, thecomponent 18 can thus fulfill the high demands in terms of service life.The flow divider 40 is simple to manufacture and easy to adapt inexisting fuel chamber hubs 18.

1.-10. (canceled)
 11. A burner arrangement for a combustion system forcombusting liquid fuels, comprising: a burner hub; an air supplychannel; and a fuel supply channel for each type of fuel, wherein thefuel supply channel is at least partially embodied in the burner hub,wherein a flow divider is arranged in the fuel supply channel, andwherein the flow divider is distanced from a wall of the fuel supplychannel so that an interspace associated with a flow path of a fuelflowing through the fuel supply channel is formed between the wall andthe flow divider.
 12. The burner arrangement as claimed in claim 11,wherein the flow divider is formed by a sleeve introduced into the fuelsupply channel.
 13. The burner arrangement as claimed in claim 11,wherein the flow divider protrudes at least partially into the annularchannel.
 14. The burner arrangement as claimed in claim 11, wherein theflow divider comprises a flow means including a flow-through opening,and a disk including a corresponding flow-through opening.
 15. Theburner arrangement as claimed in claim 14, wherein the flow means is apipe.
 16. The burner arrangement as claimed in claim 15, wherein acentral bore in a center of the flow divider is provided as theflow-through opening.
 17. The burner arrangement as claimed in claim 14,wherein the disk is provided on a first end of the flow-through means,viewed in the flow direction.
 18. The burner arrangement as claimed inclaim 17, wherein the disk is clamped to the wall in a form-fit manner.19. The burner arrangement as claimed in claim 17, wherein the diskrests on a positioning projection.
 20. The burner arrangement as claimedin claim 14, wherein the disk includes a larger first diameter than asecond diameter of the flow-through means.
 21. The burner arrangement asclaimed in claim 14, wherein the flow divider in the disk includes abore.
 22. The burner arrangement as claimed in claim 21, wherein thedisk includes a plurality of bores, which are essentially equallydistributed over the periphery.
 23. A method for operating a burnerarrangement, comprising: routing fuel during operation through the fuelsupply channel, wherein a main part of a fuel flows through a flowthrough-opening of the flow divider and a minimal part of the fuel flowsthrough an interspace of the flow divider, wherein the burnerarrangement comprises: a burner hub, an air supply channel, and a fuelsupply channel for each type of fuel, wherein the fuel supply channel isat least partially embodied in the burner hub, wherein a flow divider isarranged in the fuel supply channel, and wherein the flow divider isdistanced from a wall of the fuel supply channel so that an interspaceassociated with a flow path of a fuel flowing through the fuel supplychannel is formed between the wall and the flow divider.
 24. The methodas claimed in claim 23, wherein the flow divider is formed by a sleeveintroduced into the fuel supply channel.
 25. The method as claimed inclaim 23, wherein the flow divider protrudes at least partially into theannular channel.
 26. The method as claimed in claim 23, wherein the flowdivider comprises a flow means including a flow-through opening, and adisk including a corresponding flow-through opening.
 27. The method asclaimed in claim 26, wherein the flow means is a pipe.
 28. The method asclaimed in claim 27, wherein a central bore in a center of the flowdivider is provided as the flow-through opening.
 29. The method asclaimed in claim 26, wherein the disk is provided on a first end of theflow-through means, viewed in the flow direction.
 30. The method asclaimed in claim 26, wherein the disk includes a larger first diameterthan a second diameter of the flow-through means.